Remove cleanup when moving off UIWindow. Closes #23.

Initially, this was added to prevent retain cycles caused by SwipeAction handlers capturing self.  Instead, it should be left up to the implementor to use [weak self] in handler implementations or ensure the action view is hidden before dismissing/popping a temporary parent view controller.  I've verified this behaves the same way as UITableViewRowAction.

Source/SwipeTableViewCell.swift

@@ -113,15 +113,6 @@ open class SwipeTableViewCell: UITableViewCell {
         }
     }
 
-    /// :nodoc:
-    open override func willMove(toWindow newWindow: UIWindow?) {
-        super.willMove(toWindow: newWindow)
-
-        if newWindow == nil {
-            reset()
-        }
-    }
-
     /// :nodoc:
     override open func setEditing(_ editing: Bool, animated: Bool) {
         super.setEditing(editing, animated: animated)